Polycarbonate resins have many excellent characteristics such as excellent heat resistance, mechanical properties and electric properties and high dimensional accuracy, and therefore are widely used in a variety of fields. For example, molded products obtained by injection molding, extrusion molding or the like of polycarbonate resins are utilized for automotive materials, materials for electrical and electronic equipments, housing materials, materials for the production of parts in other industrial fields, etc.
In particular, flame retarded polycarbonate resin compositions are used as members for information/mobile devices such as computers, notebook computers, tablet terminals, smartphones and mobile phones, office automation equipments such as printers and copying machines, etc.
Recently, reduction in size and thickness of electronic equipments including the above-described information/mobile devices has been accelerated. As a member to be used, a sheet/film having high flame retardance, which is evaluated as VTM-2 or higher in the UL94 test even when the thickness thereof is 0.25 mm or less, has been desired.
For example, Patent Documents 1 and 2 describe a flame-retardant polycarbonate resin composition, wherein a phosphazene compound or a condensed phosphoric acid ester-based compound is used as a flame retardant. However, this is a composition optimized mainly for injection molding, and the viscosity of the resin component is low. In addition, since a polyfluoroethylene having fibril-forming ability, which has large shrinkage at the time of molding and poor dispersibility, is blended in the composition, it is unsuitable for the production of a film or sheet. Specifically, when this composition is molded into a film/sheet by means of a melt extrusion method, the film/sheet has a large thickness unevenness, and when a test piece having a thickness of 0.25 mm or less is subjected to the UL-94 VTM burning test, it is evaluated as non-conforming because tearing of the film during flame contact exceeds the bench mark.
Patent Document 3 describes a resin sheet, wherein a polycarbonate, a phosphorus-based flame retardant and a polyfluoroethylene are blended. However, the document does not describe any viscosity (flow value) of the resin composition. Moreover, not only a product of a polycarbonate having high flowability, but also a phosphorus-based flame retardant that increases flowability and a fibrillated polyfluoroethylene having poor dispersibility are blended in the composition of the Examples, and for this reason, a film/sheet obtained by the melt extrusion method has a large thickness unevenness. Similarly, in this case, when a test piece having a thickness of 0.25 mm or less is subjected to the UL-94 VTM burning test, it is evaluated as non-conforming because tearing of the film during flame contact exceeds the bench mark.